The majority of the known and commercially available low-pressure fluorescent discharge lamps are so-called fluorescent lamps (FLs) at present. For example, compact fluorescent lamps (CFLs) are intended to replace incandescent lamps used in a wide field of industry and home applications. In order to provide a CFL that resembles conventional incandescent lamps, a bulb shaped outer envelope may encapsulate the CFLs. The advantages of these lamps are low power consumption and long lifetime. However, one of the main disadvantages of FLs, including CFLs, is their relatively long run-up time.
A number of different solutions currently exist to improve run-up behavior, i.e., the time needed after switching on the supply for the lamp to reach 80% of its stabilized luminous flux (as defined by Energy Star Program Requirements for Compact Fluorescent Lamps 4.3: Section 2, Definition DD, Page 2). This property is also referred to as “lamp warm-up time,” which is the time needed after start-up to emit a defined proportion of its stabilized luminous flux (defined by the Commission Regulation (EC) EuP No 244/2009 Annex l/1/k). By way of example only, long-life fluorescent lamps currently need approximately 0.5 to 1.5 seconds to preheat the cathodes or electrodes before starting. Before preheating is complete, there is no light emission from the lamp. Once the arc discharge is initiated, the fluorescent lamp still requires an additional approximately 20 to 120 seconds or more to reach 80% of its stabilized luminous flux.
Prior attempts to reduce the run-up time of a FL that uses amalgam mercury dosing by incorporating an auxiliary amalgam close to one of the electrodes in the lamp. As a result of this arrangement, mercury stored in the auxiliary amalgam is vaporized shortly after switching on and in this way, the run-up period is reduced. However, one disadvantage of this proposed solution is that it does not provide an instant light feature.
Another known solution combines two lamps in one unit. More particularly, a fluorescent lamp and a conventional incandescent lamp are combined. Although it has been suggested to simultaneously turn on both lamps in order to result in instant light from the incandescent lamp, and then subsequently terminate or switch off the incandescent lamp, these known arrangements do not provide an efficient and effective manner for warming up the mercury source. For example, it has been suggested that a thermally sensitive element be located in the ballast compartment. This arrangement does not provide an accurate assessment of the actual thermal conditions of the discharge vessel. Further, locating a thermally sensitive element in a ballast compartment is potentially impacted by temperature variations caused by different illumination positions of the lamp e.g. vertically upright or inverted. As a result, the thermally sensitive element does not provide an accurate representation of the heat conditions.
Still another known solution is to apply power to the incandescent lamp only when the lamp assembly is turned on or switched on. Once a predetermined temperature is reached, the switch then de-energizes the incandescent lamp and subsequently applies power to the fluorescent lamp. The thermal switch associated with this arrangement aids in starting of the fluorescent lamp in low temperature, ambient conditions; however, it does not improve run-up of the lamp assembly.
In still another known arrangement, a fluorescent lamp is used in conjunction with a small incandescent lamp and AC power line voltage is provided. An inverter-type ballast is combined with the lamp base and is operable to power the fluorescent lamp whenever the base is received in the associated lamp socket. A thyristor or silicon controller rectifier (SCR) causes total light provided from the combination fluorescent-incandescent lamp assembly to remain substantially constant from the moment that AC power line voltage is provided at the lamp socket. When the AC power line voltage is initially provided, light from the incandescent lamp is at its maximum, while light provided from the fluorescent lamp will be at a minimum. Thereafter, light from the incandescent lamp will gradually diminish as the fluorescent lamp gradually increases. After a period, the AC power line voltage is totally disconnected from the incandescent lamp. Unfortunately, due to the SCR, the RMS value of the input power is about 70% of the nominal value and results in a specialized incandescent lamp that has increased cost and complexity.
Consequently, a need exists for a long-life fluorescent lamp that provides energy savings with instant light capabilities and fast warm-up, and overcomes the problems noted with prior proposed solutions.